Fixed 6 degrees distal femoral cut consistently achieves neutral alignment for Asians, Caucasians, and Native Hawaiian/Pacific Islanders

摘要

Background Restoration of a neutral mechanical axis (MA) is important to the success of total knee arthroplasty (TKA). While known differences are present between Asians and Caucasians regarding native knee alignment, it is unknown whether such differences exist amongst Native Hawaiian/Other Pacific Islanders (NHPI) or if utilizing a fixed distal femoral cut of 6 degrees can consistently achieve a neutral MA in these minority racial groups. This study examines the preoperative deformities presented by Asians, Caucasians, and NHPI, and the resulting knee alignment achieved following TKA when a fixed 6 degrees distal femoral cut is targeted for all patients. Methods Preoperative and postoperative MA was measured from 835 Asian, 447 Caucasian, and 163 NHPI hip-to-ankle radiographs. All patients underwent TKA in which a standard distal femoral cut of 6 degrees valgus was targeted for all patients. Data were evaluated as continuous variables and by groupings of varus (MA 3 degrees), and neutral (- 3 degrees <= MA <= 3 degrees) alignment. Results Preoperative deformity ranged from 38 degrees varus to 29 degrees valgus. The proportion of Asian and NHPI presenting with varus alignment prior to surgery was significantly greater than Caucasian patients in both males (Asians: 80.6; Caucasians: 67.0; NHPI: 79.0, p = 0.001) and females (Asians: 66.1; Caucasians: 45.7; NHPI: 63.2, p < 0.001). There was no difference in the proportion of patients (72-79) achieving a neutral MA amongst all three racial groups. Conclusion NHPI appear to have similar preoperative deformities to Asians with both groups having significantly more varus alignment than Caucasians. Despite a wide range of preoperative deformity, application of a fixed distal femoral cut of 6 degrees valgus successfully established a neutral MA equally in the majority of patients across all three racial groups.